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Jacob Klein (1734) first used the term Echinodermata for sea urchins.
Linnaeus in 1758 placed Asterias, Echinus and Holothuria under Mollusca.
Lamarck (1801) included these animals in the order Echinoderm of the Class Radiata.
In 1847 Leuckart gave phylum rank to the Echinodermata.
The Echinoderms are spiny skinned animals.
They are exclusively marine animals. They do not show distinct head.
They show pentaradial symmetry.
They show peculiar water vascular system of coelomic origin.
They are coelomate animals with pentaramous radial symmetry, that is the body can be divided into five parts arranged around a central axis, but the larva is bilaterally symmetrical.
They have an endoskeleton of calcareous ossicles made from mesoderm, there are also external spines which may be movable or fixed.
Respiratory organs are minute gills protruding out from the coelome.
There is no definite blood vascular system, it is represented only by lacunar tissue, there are no definite excretory organs.
Nervous system forms a ring around the mouth with nerves radiating from it, it is the principal nervous system and is in contact with the ectoderm in addition there is a deeper nervous system lying In the mesoderm.
Sexes are usually separate but copulation does not take place. Echinodermata have no parasitic forms.